1. Field
The embodiments relate to disk-drive automatic recognition/setting apparatus and methods.
2. Description of the Related Art
FIG. 5 illustrates the related art.
A redundant array of independent (or inexpensive) disks (RAID) system including a plurality of hard disk drives (HDDs) with a serial attached small computer system interface (serial attached SCSI or SAS) interface generally uses expander devices for attaching the HDDs. As shown in FIG. 5, expanders are located between controllers (CM0 and CM1) for controlling the RAID system and disk enclosures (DE00, DE01, and DE02) including HDDs. Expanders are used to set expanded DEs.
In a SAS environment, controllers (CMs), expanders, and HDDs form one port by attaching transmission/reception ports referred to as phys, thereby attaching the devices. This must be done by taking into consideration the setting of a routing method of each expander. There are three routing methods that can be used in expanders: direct routing, table routing, and subtractive routing. The routing method can be set for each expander phy. Direct routing is an access method for directly accessing an attached device (one-to-one attachment) according to a specified SAS address. Table routing is an access method in which SAS addresses of devices attached to an expander are stored as a plurality of tables, and, in response to a request for accessing the devices which is given by specifying the SAS addresses, reference is made to the tables, and access data and the like are distributed among the devices indicated by the SAS addresses. Subtractive routing is an access method in which, if an access-requested SAS address is not included in a routing table, its access data is transferred to a port attached to another expander. The Serial Attached SCSI-1.1 (SAS-1.1) Revision 10 defined by the American National Standards institute (ANSI) describes on page 48 that, as in expanders 10, 11, 20, and 21 shown in FIG. 5, an expander attached at host side to another expander uses subtractive routing at host side and uses table routing at the opposite side.
Referring to FIG. 5, a port containing phys 00 to 03, a port containing phys 08 to 0n, and a port containing phys 04 to 07 of an expander 00 are each represented as “T”, which indicates that the ports are routed by table routing. A port containing phys 00 to 03 of an expander 10 is represented as “S”, which indicates that the port is routed by subtractive routing. A port containing phys 08 to 0n and a port containing phys 04 to 07 of the expander 10 are represented as “T”, which indicates that the ports are routed by table routing. The similar description applies to other portions.